In the food service industry, there is a need for convenient food service containers. Such containers may take the form of plastic, fibrous, or paper dishes for serving stews, soups, salads or the like. Preferably the dish container design is such that the containers are stackable or nestable for convenient storage using a minimum of space.
Dish-like food containers may be provided with interlocking covers for use, for example, when food is to be carried off the premises. These covers in the past have been made to engage the dish for closure using various fastening means, for example, tongue-in-groove locking arrangements wherein female and male locking members are provided on the dish and/or on the cover. Certain container constructions have comprised integral bottom and cover portions which are joined at a flexible joint, which construction is popular for serving take-out sandwiches.
Dish-like containers may be fashioned such that the dish and cover are identical and their use reversible, i.e. a single dish construction may serve either as a dish, when used alone, or as a closed container, when two such dishes are used in combination by inverting one container for use as a cover for a second container. This type of structure is desirable in that it obviates the need to stock and store separate dishes and covers. Structures of this type are shown, for example, in U.S. Pat. No. 3,933,295; U.S. Pat. No. 3,620,403; U.S. Pat. No. Des. 263,684; and U.K. Patent Specification No. 1,602,694.
Reversible dish/cover containers of the type aforesaid may be provided with a circumferential or peripheral flange surrounding the open surface of the dish. When two such containers are combined to form a closed container, the surface of the respective flanges are abutted in a sealing relationship, and the tongue-in-groove arrangement interlocks the containers. One end of the flange on the reversible container may be provided with a male locking member, such as an integral tongue, and the opposed end is provided with a female locking member, such as a groove. From a nested stack of such identical containers, the dish and cover are removed as necessary, and the container to serve as cover is inverted relative to the dish container in order to align the male and female locking members for engagement.
Conventional tongue-in-groove closure arrangements for locking food containers can be ineffective in maintaining the locked relationship of the dish and its cover. Frequently, such containers are made of flexible, bendable material such as foam plastic or paper, and a force exerted on the side or top of the container may be sufficient to disengage the closure, making it difficult to transport food within the closed container.